This invention relates to the design and manufacture of contact or mechanical disturbance sensors based on the triboelectric principle.
Meryman et al (U.S. Pat. No. 2,787,784) disclose a device for detecting mechanical disturbances using a specially constructed electrical cable operating on the triboelectric principle in which the friction associated with relative motion between the several conducting and dielectric components of the cable causes electrical charge to be transferred between the conductors when the cable is disturbed. This transfer of charge can cause a small but readily detectable voltage and current when the sensing cable is connected to an amplifier.
The general object of this invention is to provide a low-cost means to manufacture triboelectric sensing devices including sensing cable and flat area-sensors. It is a specific object of this invention to provide a type of triboelectric sensor which is very thin and flexible and hence capable of being deployed inconspicuously and to conform to varied surfaces.
When used as part of a tennis line-calling system, inconspicuous deployment can involve being concealed under the surface coating of a hard-surface tennis court, being bonded to the underside of a clay court boundary marking tape or attached to a tennis net. In other applications this type of sensor could be installed under wallpaper or rugs, in upholstery, in driveways and roadways, on the outside or inside of pipes and tanks, in short, in any application where contact or mechanical disturbance is to be sensed and the sensor must be thin but otherwise may have any shape including very long (hundreds or even thousands of feet) and/or wide (up to several feet).
According to one aspect of the invention, a triboelectric sensor for detecting mechanical motion or vibration includes one or more inner electrical conductors, dielectric material surrounding said conductors, and an outer conductor made of metallic foil, surrounding the dielectric material.
According to a second aspect of the invention, the dielectric material is a plastic-coating on the metallic foil of the outer conductor.
According to a third aspect of the invention, the outer conductor is formed into a sealed tube.
According to a fourth aspect of the invention, the sensor is formed into a cable-like configuration.
According to a fifth aspect of the invention, the sensor is formed into an flat ribbon-like configuration.
According to a sixth aspect of the invention, the sensor is formed into an area sensor configuration.
According to a seventh aspect of the invention, a method for manufacturing a triboelectric sensor includes forming one or more inner electrical conductors, surrounding the conductors with dielectric material, and surrounding the dielectric material with an outer conductor made of metallic foil.
According to an eighth aspect of the invention, the surrounding said conductors with dielectric material further comprises coating said metallic foil with a plastic-coating.
According to a ninth aspect of the invention, the method further includes forming the plastic-coated metallic foil into a sealed tube by folding the metallic foil around the inner conductors, creating an open edge, and heat-sealing the open edge of the folded foil.
According to a tenth aspect of the invention, the heat sealing further includes passing an electrical current from a first electrode into the metallic foil, and passing the electrical current from the metallic foil through a second electrode.
According to an eleventh aspect of the invention, the electrodes are made largely of graphite.
According to a twelfth aspect of the invention, the method further includes forming the graphite electrodes into pencil-like elements.
According to a thirteenth aspect of the invention, the method further includes forming the sensor into a cable-like configuration.
According to a fourteenth aspect of the invention, the method further includes forming the sensor into a flat ribbon-like configuration.
According to a final aspect of the invention, the method further includes forming the sensor into an area sensor configuration.